To tell you the truth man, if you want to do any gaming, don't get a Macbook. Save yourself the money and hassle and get a gaming laptop, which you can get for under the cost of a Macbook anyways.
However, Macbooks are great machines. I personally would like to have one, but I've already got a nice laptop. If you truly want a Macbook, my 6th sense is telling me that Apple will soon refresh/update the Macbook to have the new Intel GMA X3100 gpu. While it's still not a gaming chip, its significantly better than the current GMA 950.
To answer your question, yes Warcraft 3 will run on it at about minimum settings, but playable.